There are/were several considerations:
1. My Nexus 6 shamu is still running very strong with Android 10 supported.
2. LineageOS development stopped for several months and as I have qwertz model, then the keyboard was not in usable state. (This has changed recently, so let's see ).
3. SailfishOS is like a fresh air in the world of Android. And the keyboard was easily configurable (Thanks! @Kabouik&Mosen). But my communication relies heavily on xmpp/jabber. SailfishOS has developed greatly in this aspect and in person to person chats it is OK with MAM and message carbons etc. However - still no MUC.
No ssh connection to Pro1 over wifi (fortunately usb connection worked). Wifi hotspot very unreliable - do not connect usb cable (eg. for charging) during session. No access from PC to either internal storage or sd card with usb cable. Several other small glitches here and there. Don't get me wrong - I like SailfishOS on Pro1, but I can't rely on it in my everyday life...